Automatic telephone system



1,393, 06, Patented 001-1. 18, 1921.

T. G. MARTIN.

AUTOMATIC TELEPHONE SYSTEM APPLICATION FILED OCT. 13. 1917.

UNITED STATES PATENT OFFICE.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR T0 AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Oct. 18, 1921.

Application filed October 13, 1917. Serial No. 196,384.

T 0 all whom it may concern Be it kn wn ha TA MARr a citizen of the United States of America, and resident of Chicago, Cook county, Ill1- nois, have invented certain new and useful Improvements in Automatic Telephone Systoms, of which the following is a specification.

My invention relates in general to automatic telephone systems, and is particularly well suited for use in small exchanges of this character which are commonly known as private automatic exchanges, although it might well be of utility in exchanges of any size. However, it is conceived that its principal field will be found in small private exchanges where the number of important substations requiring the special service pro vided by my invention will be large relative to the total number of stations, and where therefore the total expense in providing the necessary exchange equipment will be negligible. In brief, the object of the invention is to provide means for notifying the subscriber at a calling station (as by ringing his bell, for example,) of the response of the called subscriber, thereby rendering it unnecessary for such calling subscriber to wait on the line with the receiver to his ear.

The means employed in accomplishing the foregoing and other useful objects, will be described and explained in the specification which is to follow, reference being bad to the accompanying drawing forming a part thereof. The figure of the drawing shows a complete circuit connection between a calling substation A and a called substation A in a system embodying the principles of the invention. The connection has been est-ablished through the medium of the individual line switch O associated with the line of substation A and the connector switch D which is one of a group of connectors common to all the lines in the system.

The substation A may be of any suitable common battery type except as is hereinafter mentioned, and comprises among other details the receiver 2, transmitter 3, switch hook 4, ringer 5, and condenser 6; Being an automatic substation, there also pro vided a calling device represented herein by the impulse springs 7 and 8 and the impulse wheel 9. The calling device is of the type in which a reciprocating, dial is provided which is manually operable, in accordance with the digits in a called number to produce series of momentary interruptions in the line circuit. A calling deviceof this type is shown in the British patent to Dicker No. 29,654: Of l9l0.

In order to carry out my invention, the switch hook 4 is preferably of the three position type, being provided with a locking lever 10 which is adapted to hold the switch hook in an intermediate position when the receiver is removed. The mechanical construction of asuitable three position switch hook is shown in the application of John Erickson Serial No. 130,528, filed Nov. 10, 1916.

The line conductors 21 and 22 terminate at the exchange switchboard in the individual line or trunk selecting switch C which may be briefly described as a rotary line switch whose wipers have no normal position. A line switch of the above type is disclosed in the patent to Lamb No. 1,193,160 granted August 1, 1916. Each local line in the branch exchange is provided with a line switch similar to the line switch C and the banks of all these line switches are connected in multiple and form the terminals of trunk lines which extend to connector switches.

One of these trunk lines is shown in the drawing extending to the connector switch D, which is of the well known Strowger ver-' tical and rotary type disclosed in the patent to Keith, Erickson, and Erickson, No. 815,176, granted March 13, 1906; The mechanical construction of the switch is sub- A desires to call the subscriber at substation A, when the receiver is removed the switch hook 4 is permitted to rise about half way where it is held by the locking lever 10. In

this position of the switch hook, contact springl5 is shifted fromcontact spring 16 into engagement with contact spring 14; contact spring 12, however, remains in engagement with contact spring 13. By the shifting of the contact spring 15 the ringer 5 is disconnected and a circuit is completed over the line for the line relay 23 ofthe line switch C as follows: ground at G, resting contact of armature 34 and the said armature, line conductor 22, transmitter 3, receiver 2, impulse springs 7 and 8, switch hook springs 14, 15, 13 and 12, line conductor 21, armature 32 and its resting contact, and the winding of the line relay 23 to battery. The line relay 23 is accordingly energized and completes a circuit for the switching relay 24 as follows: ground at G armature 35 and its working contact, winding of the switching relay 24, and the winding of the stepping magnet 25 to battery. If the wipers of the line switch are standing upon contacts of an idl'etrunk line, the switching relay 24 will at once energize and extend the line conductors into'connection with the conductors of the trunk line. However, it will be assumed that the trunk line with which the wipers are associated when the call is initiated is busy, in which case there will be a ground potential upon the test contact engaged by the test wiper 27. ,Under these circumstances the switching relay 24will .be short-circuited and the stepping magnet 25 will be operated over a circuit which is closed by the line relay 23 simultaneously with the closure of the energizingcircuit for the switching relay 24. This operating circuit may be traced'as follows: grounded test contact, test wiper 27, armature 33 and its resting con-.

tact, armature 36 and its working contact, and the winding of the stepping magnet 25 to battery. Since. the stepping magnet 25 interrupts its own circuit, it will operate in the manner of a buzzer to advance the switch wipers step by step as long as the test wiper 34 ofthe switching relay 24, the line conductors 21 and 22' are disconnected from their normal connections in the line switch C and are extended by way of wipers 26 and 28 and normally closed contacts of the reversing or back bridge relay 57 to the windings of the double-wound line relay 50 of the connector D. In addition, at its armature 33 relay 24 shifts the test wiper 27 into connection with the lower terminal of its own winding thereby grounding the test contact 30 and preparing a holding circuit for itself.

Following the extension of the calling line as above described, the line relay 50 0fthe connector D is energized over the calling subscribers loop and closes the usual circuit for the slow acting release relay .51. Relay 51, upon energizing, prepares the usual circuit for the vertical and rotary magnets 58 and 59 and in addition completes a holding circuit for the switching relay of the line switch 0 as follows: ground at G armature 68 and its working contact, bank contact 30, test wiper 27, armature 33 and its working contact, winding of the switching relay 24, and the winding of the stepping magnet 25 to battery. Although it has not been previously ,so' stated, it will be understood'that the switching relay 24 is sufficiently high inresistance to prevent the op eration of the stepping magnet. It is understood, furthermore, that the holding circuit is closed at the connector switch before the slow acting line relay 23 at the line switch has had time to dee'nergize. A branch of the holding circuit extends by way of conductor 38 to multiple test contacts in the banks of the connectors which have access to the line of substation A by way of normal conductors 38 and 39 where, by a ground potential on the test contacts the line is made busy.

The foregoing operations have occurred in response to the removal of the receiver at substation A. The calling subscriber may now operate his calling device in accordance with the first digit of the number of substation A thereby producing a series of interruptions in the circuit of the line relay 50 of the connector D. The line'relay 50 is accordingly deenergized momentarily a num ber of times and at each denergization transmits an impulse to the vertical magnet 58.

as follows: ground at G armature 66 and its resting contact, armature 67 and its'working contact, winding of the low resistance slow acting private control. relay 53, winding of the vertical magnet 58 and the side switch wiper'64 in firstposition to battery. In response to these impulses, the vertical magnet operates to raise the switch shaft step by step until the wipers 90, 91, and 92 stand opposite the required horizontal level of bank contacts. Relay 53 is energized in series with the vertical magnet and being slow acting retains its armature attracted during the series of impulses to close an energizing circuit for the private magnet 60. At the end of the vertical movement of the switch, relay 53 and the private magnet are deenergized, the latter controlling the side switch wipers in the usual Way to advance them to their second position.

The calling device at substation A may now be operated in accordance with the final digit of the number to produce another series of interruptions in the circuit of the line relay 50. Now however, the side switch Wiper 64: being in its second position, the line relay 50 will be operated to transmit a series of impulses to the rotary magnet 59 in a manner which will be readily understood. By the operation of the rotary magnet, the wipers 90, 91, and 92 are rotated step by step until they come to rest in engagement with bank contacts 93, 9e, and 95 respectively. The relay 53 and the private magnet are operated as before and at the end of the rotary movement of the switch the deenergization of the private magnet causes the side switch wipers to be advanced to their third position, it being assumed that the line of substation A was idle when called.

I When the side switch wiper comes into engagement with its third position contact point, a circuit is completed for the switching relay 24 of the line switch C as follows: ground at G, side switch wiper 65 in third position, test wiper 91, bank contact 94, winding of the switching relay 524 and the winding of the stepping magnet 25 to battery. Due to a mechanical locking arrangement controlled by the line relay 23 of the line switch (explained in the previously mentioned patent to Lamb) the switching relay 2% is not completely operated but attracts its armature only far enough to clear the called line of its normal battery and ground connections in the line switch. Ground G of course, also extends to the multiples of contact 94: in the banks of the other connectors and thereby makes the called line busy. A branch circuit also er;- tends from the conductor joining the side switch wiper 65 and the test wiper 91 by way of'the Winding of the switching relay 56 and the side switch wiper 64 in third po sition to battery. Relay 56 is therefore energized and by operating its armatures 79 and 80 completes a signaling circuit which may be traced as follows: ground at G, the ringing current generator, contact of the interrupter mechanism IR, resting contact of the armature 7 6 and the said armature, armature 80 and its working contact, wiper 92, bank contact 95, line conductor 22, through the ringer and condenserat substation A, line conductor 21, bank contact '93, wiper 90, working contact of armature notify the subscriber that he is being called.

It is understood that the ring cut-01f relay 55 is so adjusted that it will not energize until the receiver at the called station is removed from the hook.

The connection to the called line has now been completed and the ringer at the called substation is being actuated to signal the called subscriber. It will be convenient now to consider the means by which the calling subscriber may be notified when the called subscriber responds. It will be observed that the lower winding of the line relay 50 is not connected direct to ground as is usual, but is connected to ground in series with relay 52 which, however, is normally short-circuited at the armature 78 of the switching relay 56. Then the connection to the called line is completed and the relay 56 is energized, this short-circuit is removed and relay 52 is operated to close a contact in the talking circuit at its armature 69. Suppose now that the calling subscriber does not wish to wait with the receiver to his ear until the called man answers. In this case he will release the loclc ing lever 10 by hand, whereupon the switch hook is permitted to rise to its final position. The receiver may be placed on any con venient support. In the final position of the switch hook, the contact spring 12 is disengaged from the contact spring 13 and is brought into engagement wit-h contact spring 11 thereby inserting the resistance 18 in the line circuit in series with the trans mitter and receiver. The ringer 5 and condenser 6 are also connected across the line. When the resistance 18 is inserted in the line, current flow is sufiiciently reduced to cause the deenergization of the relay 52 which it should be mentioned is of comparatively low resistance and is marginally adjusted. The line relay 50, however, remains energized. Upon deenergizing, relay 52 opens the lower heavy talking conductor and prepares a circuit for operating the ringer 5 at the calling substation which will be traced shortly. Circuits of the calling and called substations and the circuit of the connector D are now inthe condition shown in the drawing. The ringer at substation A is being actuated and the ringer at the calling substation A is bridged across the line ready to be operated when the called subscriber answers his telephone.

When the receiver is removed at the called substation A, the switch hook rises to its intermediate position and shifts the contact spring 15, with the result that the transmitter and receiver are connected in bridge of the line. The ring cut-off relay 55 at the connector is now energized and at its armature 7 4i completes a locking circuit for itself as follows: ground at G off-normal contact 62 (closed at the first upward movement of the switch shaft), working contact of armature 7a and the said armature, and the up per winding of relay 55 to battery. The above circuit also serves to supply ground to the lower winding of back bridge relay 57. As a further result of its energization, relay 55 disconnects its own lower winding and the'lead from the ringing machine at its armatures 77 and 76 respectively, and closes normally open contacts in the heavy talking conductors. A still further result of the energization of relay 55, is the closure of a signaling circuit for the calling subscriber as follows: ground at G the ringing current generator, working contact of armature 75 and the said armature, resting contact of armature 69 and the said armature, bank contact 31, line wiper 28, working contact of armature 34 and the said armature, line conductor 22, ringer 5,

' condenser 6, contact springs 11 and 12 to line conductor 21. The return circuit is completed by way of line conductor 21, armature 32 and its working contact, wiper 26 to bank contact 29, and thence through the lower winding of line relay and relay 52 in series to ground (relay 5'? being now energized) and also through the upper condenser and upper winding of relay 57, and the battery to ground. Current flow over the above circuit will be sufficient to operate the ringer 5 without however, interfering with the continued energizatlon of the line relay50 which is held up by direct current through the resistance 18 at the substation, and without causing the relay 52 to vibrate its armature, for this relay is provided with a slug of copper to make it slow to energize.

When the calling subscriber hears his bell ring, he will know that the called party has answered and will immediately restore his switch hook to its intermediate or talking position thereby cutting out the ringer 5 and short-circuiting the resistance 18. The relay 52 at the connector is now energized again and at its armature 69 disconnects th ringing generator from the line and completes the talking circuit. The appa: ratus is now in proper condition for conversation. Current for the transmitter at the substation A is supplied through the windings of the line relay 50 (in series'with the low resistance relay 52) while current for the transm ter at t e u station A is A, line relay 50 is deenergized, followed by V the de'elnergization of the slow acting release relay 51, and a circuit is thus completed through the release magnet 61 as follows: ground at G armature 68 and its resting contact, off-normal contact 63, and th winding of the release magnet 61 to battery. By the energization of the release magnet, the connector D is restored to normal in the usual and well understood manner. Relay 51 upon deenergizing, also breaks the holding circuit extending back to the switching relay 24 of line switch C, thereby permitting this relay to deener ize and restore the circuits of line switch to their normal condition.

The operation of the connector D in calling a busy line, is the usual one and will require no detailed explanation. It will be sufficient to say that when the relay 53 deenergizes at the end of the rotary movement of the switch, it the called line is busy, the test relay 54: will be energized over the private wiper circuit in series with the private magnet 60, the latter being held energized to lock the side switch wipers in their second positions. In it's energized po sition the test relay 54L completes a locking circuit for itself and the private magnet at its armature 72 and at its armature 73 connects the lead from the busy signaling machine Q to the lower heavy talking conductor. Being advised by the busy signal thus transmitted to him that the called line is for the time being inaccessible, the calling subscriber will replace his receiver and the switches in use will be restored to normal.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

1. In a telephone system, subscribers lines, talking equipment therefor, a call signal at the station on each line for receiving calls, automatic switching mechanism controlled from a calling station for connecting with a called station and for actuating the signal thereat, and means for actuating the call signal at the calling station when the called subscriber answers. I

2. In a telephone system, a calling and a called subscribers line, acalling device at the calling station, switching mechanism at the exch ge controlled by said device after the receiver is removed from the hook for connecting said lines and for signaling the called line, means associated with said switching mechanism for preparing a circuit for signaling the calling station while the receiver is oil the hook, means at the substation operated at the option of the call-- ing subscriber for controlling said first means, and additional means at the exchange for closing said signaling circuit when the called subscriber answers.

3. In a telephone system, a calling and a called subscribers line, switching mechanism at the exchange controlled by the calling subscriber for connecting said lines and for signaling the called subscriber, means associated with said switching mechanism for signaling the calling subscriber when the called subscriber answers, and means at the calling station operable at the option of the calling subscriber for determining in advance whether he will be signaled or not.

41-. In a telephone system, a calling and a called subscribers line, automatic switching mechanism for connecting said lines and for signaling the called subscriber, means for inserting a resistance in the line circuit at the calling station, means associated with said switching mechanism responsive to the inclusion of the resistanace for preparing a signaling circuit for the calling subscriber, and means for closing said circuit when the called subscriber answers.

5. In a telephone system, a calling and a called subscribers line, automatic switching mechanism for connecting said lines and for signaling the called subscriber, means for inserting a resistanace in the line circuit at the calling station and for preparing a circuit for the reception of a signal, means associated with said switching mechanism responsive to the inclusion of the resistance for closing another contact in said signaling circuit, and means for completing said circuit when the called subscriber answers.

6. In a telephone system, a calling and a called subscribers line, automatic switching mechanism for connecting said lines and for signaling the called subscriber, a three position switchhook at the calling station having ringing and talking positions and a third position, means at the exchange responsive to the advance of the said switch hook to third position for preparing a circuit for signaling the calling subscriber, and means for closing said circuit when the called subscriber answers.

7. In a telephone system, a calling and a called subscribers line, automatic switching mechanism for connecting said lines and for signaling the called subscriber, a three position switch hook at the calling station having ringing and talking positions and a third position, manually operated means for advancing the switch hook to third position to alter the substation circuits, means at the exchange actuated upon the alteration of said circuits to prepare a signaling circuit for the calling line, and means for closing said circuit when the called subscriber answers.

8. In a telephone system, subscribers lines, a signal for each line, a source of current, switching mechanism controlled from a calling line for connecting with a called line and for applying current from said source to actuate a signal on the called line, and means for applying current from said source to actuate the signal on the calling line when the called subscriber answers.

9. In a telephone system, subscribers lines, a signal for each line, a source of current, switching mechanism controlled from a calling line for connecting with a called line and for applying current from said source to actuate a signal on the called line, and means responsive to the called subscriber for disconnecting said source of current from the called line and connecting it to the calling line, and means controlled by the calling subscriber for disconnecting said source of current from his line.

10. In a telephone system, subscribers lines, a signal for each line, a source of current, switching mechanism controlled from a calling line for connecting with a called line and for applying current from said source to actuate a signal on the called line, and means controlled by the called subscriber for disconnecting said source of current from the called line and for connecting it to the calling line. Y

11. In a telephone system, a calling and a called subscribers line, switching mechanism at the exchange controlled by the calling subscriber for connecting with said lines and signaling the called line, and means for signaling the calling line when the called subscriber answers and before conversation is started, said signal continuing until cut off by the calling party.

12. In a telephone system, a calling and a called subscribers line, switching mechanism at the exchange controlled by the calling subscriber for connecting said lines and for signaling the called subscriber, a relay associated with said switching mechanism and controlled by the calling subscriber to prepare a circuit for signaling the calling subscriber, another relay, said other relay conrolled by the called subscriber to close said circuit to continuously signal the calling subscriber until stopped by the calling subscriber.

13. In a telephone system, a calling and a called line, means controlled by the calling subscriber for connecting said lines and for signaling the called line, automatic means responsive to the removal of the receiver on 130 the called line when the called subscriber to the calling line when the called subscriber answers for giving the calling subscriber an answers and until stopped by the calling 10 audible signal which continues until cut off subscriber. v

by the calling subscriber. I Signed by me at Chicago, Cook county, 14. In a telephone system, a calling and a State of Illinois, this 9th day of October,

called line, means for connecting said lines 1917. i

and for signaling the called line, and automatic means for applying an audible signal TALBOT Gr. MARTIN. 

